The boy’s father, Christopher Berry, 22, of Lowell, pleaded not guilty Monday in Lowell District Court to charges of ­assault and battery on a child causing substantial bodily injury, Guyotte said.

Prosecutors said at the time that they would pursue more serious charges against Berry if the child died.

Berry, an Army veteran being treated for post-traumatic stress disorder, called 911 when he found his son limp and unresponsive, with blood bubbling from his nose and mouth. He was the only one home with the infant when the injuries ­occurred, authorities said.

Guyotte said Berry
shook the ­baby with such force that it caused extensive and catastrophic brain injuries.

Berry’s lawyer, Robin Gagne, said he had spent more than three years in the military, and now serves in the National Guard. Berry is being treated for anxiety, she said.

Prosecutors said Berry ­already faced several other charges, including breaking and entering and animal cruelty.

Guyotte said an autopsy on the baby has been conducted by the medical examiner’s office. The results on the cause and manner of death are not expected for several months, she said.

Berry will be in court on June 6 for a probable cause hearing.

The case is being inves­tigated by State Police ­assigned to the district attorney’s office and Lowell police.